The invention relates to the construction of the structural framework of a building or other structure of reinforced concrete, and particularly to column and beam forms which would become integral parts of the structural framework and to methods of employing such forms.
In the past, there have been many systems for fabricating structural frameworks, including the use of steel frameworks for industrial type buildings because they are comparatively inexpensive to build and can be assembled rapidly. Such buildings, however, face a serious problem in their relatively low fire ratings, since a fire can cause rapid expansion of steel columns and beams, resulting in twisting and warping which may result in the necessity of complete replacement of the building.
Reinforced concrete offers substantial advantages over steel from the standpoint of fire rating, and many specially designed concrete forms for such use have been proposed in the past. Some such forms are made of construction grade lumber and plywood which must be assembled into predetermined shapes for receiving poured concrete. Forms which are to be used multiple times may also be made from metals having the necessary rigidity and strength to support the weight of the fluid concrete during its pouring and initial stages of curing. These forms are made in many types and shapes, and are provided with a variety of means for locking them in position for the pour and unlocking to facilitate their removal after the concrete is sufficiently hardened.
Removable forms in general can be characterized as relatively expensive in terms of both capital cost and use, having in mind that they must be cleaned or otherwise reconditioned after each use, as well as transported from site to site. Indeed, their initial cost is usually such that it can be justified only on the basis of multiple uses, thereby reducing their per building cost.